Study of ultracold molecules promises important prospects such as novel control of chemical reactions and molecular collisions, precision measurement of fundamental physical properties, and new methods for quantum information processing and simulations of quantum states of matter. A variety of chemically interesting molecular species can be prepared in a single internal state at temperatures of a few milliKelvins. Located in a magnetic trap and polarized under a uniform electric field, these molecules now allow explorations of low-energy scatterings near the quantum threshold and they will be subject to studies of collision and reaction dynamics that are dominated by long-range, anisotropic dipolar interactions.

A quantum degenerate gas of polar molecules will greatly facilitate these activities. Towards this goal, we start with an ultracold dual atomic gas mixture near quantum degeneracy, in collaboration with D. Jin. Combing Feshbach resonance and optical Raman transfer, we achieve highly efficient, fully coherent conversion of the ultracold Rb-K atom pairs to polar molecules in their absolute ro-vibrational ground state. The resultant molecular gas has basically the same phase space density as the original dual-species atomic gases, with a trapped density of 1012 cm-3 at a temperature of 300 nK and a measured permanent electric dipole moment of 0.5 Debye. A very exciting time ahead indeed.